1. Field of the Invention
The present invention relates to systems for the reception of guidance commands for missiles, such as ground-to-air missiles, guided in optoelectronic mode, i.e. for missiles receiving guidance data, transmitted by means of laser beams, from remote firing control stations.
The term "guidance" shall be understood in its widest sense, i.e. as covering beam-riding guidance or simple remote control, in which the guidance is done by following the beam, as well as the off-beam guidance modes (sometimes designated by the term "remote control" in its strictest sense) wherein the beam is not followed, in which case the missile firing control and target firing control directions are not colinear.
2. Description of the Prior Art
The wavelengths used for the transmission of a guiding control signal in optoelectronic mode are optical wavelengths, typically in the infrared range (wavelengths generally between 12 .mu.m and 0.8 .mu.m) in contrast with the signals transmitted by using wavelengths in the radio-frequency range.
When optoelectronic guidance is used, there is the problem of disturbances introduced by the hot gas jets of the missile during its propulsion phase.
During this propulsion phase, the hot gas jets may produce disturbances capable of significantly affecting the guiding infrared beam that goes through the hot gas jets and the surrounding zone. This problem relates to direct disturbances (infrared emission proper to the propellant) as well as indirect disturbances (turbulence created in the environment producing variations in the refraction index, absorption and scattering of the beam by smoke etc.).
These disturbances, notably atmospheric disturbances, appear throughout the band of the usable wavelengths. To reduce the influence of these disturbances to the minimum, it is therefore necessary to move the sensors away, transversally, as far as possible from the axis of the missile, and hence from the axis of the hot gas jets.
FIG. 1 shows a missile, provided with infrared sensors 2 receiving an optical signal conveyed by a beam 3. To prevent the disturbances in a zone 4 around the hot gas jets from the propellant, the sensors 2 are generally mounted at the ends of fins or control surfaces 5 of the missile.
However, notably for reasons of convenience of storage, the span of the fins or control surfaces of present-day missiles is generally reduced to the minimum. This therefore means that the transversal distance obtained by positioning these sensors at the end of a fin or control surface will be always small and, in practice, inadequate.
One of the aims of the invention is to propose a system enabling the receivers to be moved away to a greater distance from the hot gas jets of the missile while, at the same time, causing the least possible disturbance to the aerodynamic characteristics of this missile.
This latter condition especially rules out the use of telescopic rods or similar devices, at the end of which the sensor would be placed.
In effect, in view of the high speeds (over Mach 3) of modern missiles, the bending stresses exerted on such rods owing to their inherent drag would be such that only thick rods could withstand these stresses. Owing to their inherent drag, these rods would then substantially influence the aerodynamic characteristics of the missile.
To resolve this difficulty, the present invention proposes, essentially, the removal to a distance, by aerodynamic effect, of the optical transducer or transducers, by mounting the sensor on an aerodynamic carrier designed so as to move away from the body of the missile, at least during the propulsion phase of this missile.